1. Field of the Invention
The invention relates to a polarization-influencing optical arrangement, in particular in a microlithographic projection exposure apparatus.
2. Prior Art
Microlithography is used for producing microstructured components, such as, for example, integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure apparatus comprising an illumination device and a projection lens. The image of a mask (=reticle) illuminated via the illumination device is in this case projected, via the projection lens, onto a substrate (e.g. a silicon wafer) coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection lens, in order to transfer the mask structure to the light-sensitive coating of the substrate.
Various approaches are known for setting specific polarization distributions in the pupil plane and/or in the reticle in a targeted manner in the illumination device for the purpose of optimizing the imaging contrast. In particular, it is known, both in the illumination device and in the projection lens, to set a tangential polarization distribution for high-contrast imaging. “Tangential polarization” (or “TE polarization”) is understood to mean a polarization distribution for which the oscillation planes of the electric field strength vectors of the individual linearly polarized light rays are oriented approximately perpendicularly to the radius directed to the optical system axis. By contrast, “radial polarization” (or “TM polarization”) is understood to mean a polarization distribution for which the oscillation planes of the electric field strength vectors of the individual linearly polarized light rays are oriented approximately radially with respect to the optical system axis.
In particular, it is known to arrange corresponding polarization-influencing elements or arrangements based on the use of linear or circular birefringence in a pupil plane of the illumination device or of the projection lens or in the vicinity thereof.
With regard to the prior art, reference is made merely by way of example to WO 2005/069081 A2, WO 2005/031467 A2, DE 101 24 566 A1 or WO 2006/077849 A1.
Depending on the concrete use situation, however, the problem can occur that the retardation provided by the polarization-influencing element of the arrangement is dependent on the propagation direction of the electromagnetic radiation in the (linearly or circularly) birefringent material and thus on the angle of incidence of the electromagnetic radiation on the polarization-influencing element or arrangement. In this connection, with regard to the prior art, reference is made by way of example to DE 10 2007 059 258 A1.
Different angles of incidence of the electromagnetic radiation can occur in particular when the relevant polarization-influencing element or arrangement is not used within the first pupil plane of the illumination device in the light propagation direction (through which the light rays still pass in a parallel fashion), but rather is positioned for example for rotating the polarization direction in a downstream plane (for example in a downstream pupil plane of the illumination device or else in a pupil plane of the projection lens) in which an angular distribution of the light rays that pass through the polarization-influencing element or arrangement is present.
A further problem that occurs using polarization-influencing elements or arrangements in a microlithographic projection exposure apparatus is that the polarization-influencing effect of the element or arrangement is generally dependent on the polarization state of the electromagnetic radiation passing through the element or arrangement, wherein different illumination settings can be set depending on the application e.g. in a first pupil plane in the light propagation direction.
The above-described situations of different propagation directions or angles and different input polarizations of the light rays passing through a polarization-influencing element can occur for example if e.g. for compensation or minimization of 3D mask effects or for targeted minimization of the retardation or sp splitting in the illumination device for instance (instead of an actually desired illumination setting with TE polarization or tangential polarization distribution) an illumination setting with TM polarization or radial polarization distribution is set and is intended to be converted into the actually desired TE polarization distribution in the further course of the beam path (e.g. downstream of the mask). Another possible scenario is the compensation of lifetime-induced birefringence effects.
Furthermore, it is also possible generally in a projection exposure apparatus that an initially present polarization state, possibly set in a targeted manner, can be influenced by polarization-influencing effects (e.g. stress birefringence induced by mount components in the material of the optical components such as e.g. lens elements, influence of dielectric layers, intrinsic birefringence in the material of optical components etc.), wherein the production of a desired output polarization distribution is additionally made more difficult by the abovementioned polarization dependence of the effect achieved by the polarization-influencing element or arrangement.